1. Technical Field
The inventive concept relates to an oscillator, and more particularly, to an oscillator including a plurality of complementary differential amplifiers.
2. Discussion of the Related Art
A phase locked loop (PLL) is a control system that generates a signal that has a fixed relation to the phase of a “reference” signal. An analog PLL includes a phase detector, a low pass filter and a voltage-controlled oscillator (VCO) placed in a negative feedback closed-loop configuration, for example. The VCO, which creates an output frequency of the PLL, is an important element for determining the performance of the PLL.
In semiconductor devices, multi-phase clocks may be used to obtain a high bandwidth. The VCO may generate multi-phase clocks, which have constant intervals, by varying its output frequency according to a control voltage. A VCO that functions as a multi-phase clock generator is configured with a separate divider or pull-swing converter to stabilize the clocks, for example.
Accordingly, there exists a need for a VCO that can stably generate multi-phase clocks by itself.